Dynamics and Surface Propensity of H⁺ and OH⁻ within Rigid Interfacial Water: Implications for Electrocatalysis

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä

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en

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7

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Journal of Physical Chemistry Letters, Volume 12, issue 41, pp. 10128-10134

Abstract

Facile solvent reorganization promoting ion transfer across the solid−liquid interface is considered a prerequisite for efficient electrocatalysis. We provide first-principles insight into this notion by examining water self-ion dynamics at a highly rigid NaCl(100)−water interface. Through extensive density functional theory molecular dynamics simulations, we demonstrate for both acidic and alkaline solutions that Grotthuss dynamics is not impeded by a rigid water structure. Conversely, decreased proton transfer barriers and a striking propensity of H₃O⁺ and OH⁻ for stationary interfacial water are found. Differences in the ideal hydration structure of the ions, however, distinguish their behavior at the water contact layer. While hydronium can maintain its optimal solvation, the preferentially hypercoordinated hydroxide is repelled from the immediate vicinity of the surface due to interfacial coordination reduction. This has implications for alkaline hydrogen electrosorption in which the formation of undercoordinated OH⁻ at the surface is proposed to contribute to the observed sluggish kinetics.

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R.K. is supported by the School of Chemical Engineering of Aalto University through a doctoral scholarship. The authors thank Heikki Lappalainen for assistance. Computational resources were provided by CSC – IT Center for Science, Finland.

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Kronberg, R & Laasonen, K 2021, 'Dynamics and Surface Propensity of H⁺ and OH⁻ within Rigid Interfacial Water: Implications for Electrocatalysis', Journal of Physical Chemistry Letters, vol. 12, no. 41, pp. 10128-10134. https://doi.org/10.1021/acs.jpclett.1c02493